500
Why is the oxygen that makes up the atmosphere found as an element, but in the Earth and in the ocean it is found as a compound? Think in terms of the state of matter of the oxygen in each situation.
In the atmosphere oxygen exist as a gas, where the particles of matter are far apart. In the solid Earth and in the ocean, oxygen exists as a solid or a liquid, where the particles of matter are closer together and are more likely to form compounds.